Nonleafing aluminum paste and method of making same



Patented Jan. 26, 1943 2,309,311 NoNLEArrNG um ras'rs AND METH- on or MAKING SAME Gordon M, Babcock, Louisville, Ky., assignor to I Reynolds Metals Company, New York, N. Y., a

corporation of Delaware Application October 9, 1940, Serial No. 380,501

No Drawing.

12 Claims. (cl. roe-m) This invention relates to metallic pigments for use in the preparation of polychromatic coatings or finishes and non-leaflng aluminum metallic finishes. and more particularly to non-leaflng aluminum pastes and their methods .of manufacture.

It has been known for some time that a nonleaflng flnish can be prepared by carefully grinding an ordinary leailng pigment, in the form of a powder or a paste, either in a liquid carrier or solvent which is compatible with the coating base with which the pigment is adapted to be used, or in the base itself. Such a grinding operation so alters the surface of the pigment by mechanical action as to make it non-leaflng. The grinding, however, not only increases the length of time required for. and the cost of, preparation of the pigment or paint, but also constitutes a fire hazard when the pigment is ground in powder form.

It is therefore the object of the present invention to provide a new and improved method of producing a non-leaflng aluminum paste which avoids the necessity for grinding, and wherein the deleaflng action is brought about by chemical, rather than mechanical, means.

Inasmuch as the paste produced by the method herein disclosed is itself of novel composition,

terials of the group comprising (a) the salts or soaps of lead, zinc and calcium. and (b) the highly polar active alcohols, esters, ketones, a1dehydes and the like. In commercial production, it is preferred to use a lead, zinc or calcium salt or soap as the deleailng agent because of the rapidity of the deleafing action of these compounds,

and the fact that supplies thereof of uniformly high quality canbe readily obtained on the open market at relatively low cost. Of the metal soaps, the naphthenates, resinates, linoleates and tungates are most suitable for. the purposes of the invention, although lead compounds such as tetra-ethyl lead, lead laurate, lead palmitate and other lead salts or soaps which are soluble in the paste carrier are also useful.

The thinner or carrier of the paste may be selected as desired from among the many available,

I having due regard to its compatibility with the the invention also encompasses the product as well as the process by which it is made.

Thebasis of the present invention resides in the discovery that certain highly polar materials, especially when in solution, have the property of chemically destroying the leaflng characteristicsof otherwise full leaiing aluminum powder when combined with such powder in the form of a paste. It is believed that the deleailng action of the polar active material is due to a rearrangement of the orientedmolecules of stearic acid already present on the flakes of the powder, so i that, by virtue of what is thought to be a prefer- ,entiitl wetting" action, the surfaces of the powder particles are readily wetted by the vehicle with which the paste so made ismixed; It has been found that a paste of this character disperses more readily than others when mixed with, the base of a polychromatic paint, enamel or lacquer finish, and also gives greater covering since the wetting" process tends to minimize agglomeration. I

In general, the preferred method of themesent invention consists in simply adding to a regular, full leaflng aluminum powder a suitable thinner or carrier in which has been incorporated adeleailng agent consisting of one or more macoating base to which the paste will ultimately be added, although it is generally preferred to use either xylol or toluol because of the wide range of 1 paints, lacquers, enamels and the like with which they are-compatible. The group of suitable carrlers also includes the straightchain hydrocarbon thinners marketed as mineral spirits.

kerosene, gasoline, petroleumnaphtha, and the like, as wellas aromatic thinners such as benzol and coal tar naphthas, and hydrogenated petroleum naphthas containing high percentages of aromatics.

The following is one example of a working formula which has proven to be quite successful in practice in producing a non-leaflng aluminum paste according to the present invention:

Pounds Aluminum powder (fully polished and leaflng) Lead naphthenate solution (24% lead)--- 1 Xylol 33. 5 Alcohol 0. 5

The use of the small amount or 51001101 in addition to the lead naphthenate solution increases the speed of the deleaflng reaction, which result could also be accomplished by increasingrthe relative quantity oflead naphthenate. The speed of reaction may also be decreased by diminishing the relative proportions of the deleaflng agents. If desired, a zinc or calcium salt or soap may be substituted for the corresponding lead compound in the foregoing formula; and in the same relative proportion, although the reaction with zinc with the coating in which the paste is to bedispersed'.

A typical formula for a paste wherein the deleafing action is produced by the use or a highly polar active organic material alone is as follows:

Pounds Aluminum powder (fully polished and leai- 7 ing) 60 Ethyl aceta Toluol 20 This formula may be varied by substituting for the ethyl acetate such other highly polar materials as methyl, ethyl or butyl alcohol, butyi acetate, ethyl lactate, acetone, etc., the speed of the reaction b'eing largely dependent upon the amount of the acetate or. other. deleaflng agent relative to that'of the toluol or whatever other thinner may be used compatibly with the color base.

In practicing the method of the present invention, the usual procedure is to first dissolve or suspend the deleaflng agent or agents in the thinher or carrier, and then add to the liquid mixture thus formed the leafing powder to form a paste. In some instances, however, it may be preferred to simply add the deleaflng agent to a previously formed paste composed of leafing powder and carrier.v Under normal conditions of temperature, pressure, humidity and the like, the leafing characteristics of a paste conforming to the first formula above recited will, be almost completely, if not entirely, destroyed in less than 48 hours after the paste has been formed. This time may be decreased by varying the proportions and/or materials of the deleafing agents, as above :indicated, or by increasing the temperature at which the mixture of carrier and deleafing agent or agents is permitted to act upon the leafing aluminum pigment. Agitation oi" the materials when forming the paste, or agitation of the paste itself, will also decrease the time required for the deleafing reaction.

There is thus provided bythe present invention a novel, simple and economical method oi producing a non-leafing aluminum paste which is susceptible of direct dispersion in a wide variety of coating bases for the production of polychromatic finishes. The paste, which is also novel in composition, may be directly dispersed in a color base to produce a non-leafing polychromatic coating without the necessity for grinding or otherwise treating the material to render it. non-leafing. Not only does a paste prepared in accordance with the present invention disperse more rapidly in the coating base and provide greater covering than ordinary leafing materials,

but it has also been found that, because of the fact that the pigment is all within the film, rather than partially on top thereof, it can be applied without giving rise to the well-known, objectionable smudging effect whichresults when some object is accidentally drawn across the air dried surface of the paint.

Although the method of preparing, and the composition of the non-leafing paste of the present-inventio'n have been described herein in some detail, and two specific formulae have been set powder forth as exemplary of its-practical application, it is to be expressly understood "that the invention is not limited to the particular examples given, but that the ingredients of the paste, their relative proportions and the 'particulanmode of preparation of the paste may be varied within limits which will be clearly apparent to those skilled in the art without departing from the underlying concept of the invention. Reference is therefore to be had to the appended claims for a definition or the scope of the invention.

What is claimed is:

1. A method of making a non-leafing aluminum paste from a normally-leafing aluminum powder while retaining the shape and size or the aluminum particles which consists in combining without grinding a suitable thinner, a deleafing agent composed of at least one material selected from the group consisting of the soaps of lead, zinc and calcium, and a normally leafing aluminum powder in such proportions as to form a paste, the leafing characteristics of said powder being substantially destroyed by the chemical action of the deleafing agent.

2. A method of making a. non-leafing aluminum paste from a normally-leafing aluminum powder while retaining the shape and size of the aluminum particles which consists in combining I without grinding asuitable thinner, a, deleafing agent composed of an alcohol and at least one material selected from the group consisting of the soaps of lead, zinc and calcium, and a normally leafing aluminum powder in such proportions as to form a paste, the leafing characteristics of said powder being substantially destroyed by the chemical action of the deleafing agent.

3. A method of making a. non-leafing aluminum paste from a normally-leafing aluminum powder while retaining the shape and size 01 the aluminum particles comprising the steps oi dissolving or suspending in a suitable thinner a deleafing agent composed of at least one of the groups consisting of the soaps of lead, zinc and calcium, and then combining without grinding the liquid mixture thus formed with a normally leafing aluminum powder to form a paste, the leafing characteristics of said powder being substantially destroyed by the chemical action of the deleafing agent.

aluminum particles comprising the steps of dis-' solving or suspending in a suitable thinner a deleaflng agent selected from the group consisting of the soaps of lead, zinc and calcium and then-combining without grinding the liquid mixture thus formed with a normally leafing aluminum-powder to form a paste, the leafing'characteristics of said powder being substantially dewhile retaining the shape and size of the stroyed agent.

I 6. In the preparation of a non-leaflng aluminum paste from a fully leaflng aluminum powder willie retaining the shape and size of the aluminum particles, the step of chemically destroying the leaiing characteristics of said powder by the chemical action of the deleaflng calcium.

'1. In the preparation of a non-leaflng alumiiully leaflng aluminum pownum paste from a v and size of the carrier containing a deleaflng agent composed of at least one of the groups consisting of the soaps of lead, zinc and calcium.

9. In the preparation of a non-leaflng aluminum paste from a fully leaflng aluminum powder while retaining the shape and size of the aluminum particles, the step of chemically dethe step of chemically delacquers, consisting stroying the leaflng characteristics of said powder which consists in combining the powder with a liquid carrier containing a deleaflng agent consisting of lead naphthenate and alcohol.

10. An aluminum manufacture of non-leafing paints, enamels and lacquers, consisting of a normally leaflng aluminum powder whose leafing film is mechanically left intact, a thinner, and at least one deleafing material selected from the group consisting of the soaps of'lead, zinc and calcium, the aluminum powder constituting more than of the total weight of the paste.

11. An aluminum paste adapted for use in the manufacture of 'non-leaflng paints, enamels and of a normally leafing aluminum powder whose leaflng film is mechanically left intact, a thinner, and a deleaflng agent comprising material selected from the group consisting of the soaps of lead, zincvand calcium, and also comprising alcohol, the aluminum powder constituting more than 50% of the total weight of the paste.

12. An aluminum paste adapted for use in the manufacture of non-leaflng paints, enamels and lacquers, consisting of the following materials in substantially the designated proportions by weight: a normally leaflng aluminum powder whose leailng film is mechanically left intact a thinner 33.5%, and a deleafing agent 1.5%, said deleaflng agent consisting of a lead naphthenate solution and alcohol.

GORDON M. BABCOCK.

paste adapted for use in the 

